This is a report on the third year and a proposal for the fourth of a five-year NICHD Population Center Grant. The interests and funded research projects of the 30-odd members fall into four main categories with a few exceptions: historical demography of the U.S., particularly around 1900; fertility levels and differentials, especially in the U.S. and developing countries; human ecology, e.g., residential patterns of different immigrant groups; and mathematical and statistical models in demography. It is proposed that core support for several population-related projects be continued, primarily in the form of staff support, summer salary for faculty, library purchases, computer time, and a colloquium series. A description is given of each of the funded projects of 1978-79 and anticipated for 1979-80.